The present invention relates to means for straightening articles by repeated reversed elasto-plastic bending and more particularly to paired-roll straightening machines used for straightening such articles as rolled shapes, shaped and round tubes, and rolled section stock.
Known in the art are paired-roll straightening machines comprising a number of stands with driving shafts installed therein in pairs and carrying rolls forming passes corresponding to the cross section of an article being straightened. All pairs of rolls are installed in stationary stands in such a manner that the passes formed thereby are located in a wavy line.
During the straightening of articles in these machines the number of bends given to an article and determining the quality of straightening is limited by the number of roll pairs 7-9. This limitation substantially reduces the efficiency of the machines of similar design and makes them unable to gain the required quality of straightening. On the other hand, increasing the number of roll pairs is restricted by the rational dimensional limits of the machines and the amount of energy spent for straightening an article.
Also known are paired-roll straightening machines with rocking stands performing circular motion (see, for example, Patent Nos. 1,017,447 and 1,205,797 issued in the Federal Republic of Germany). Each of the rocking stands in these machines comprises a frame, rolls, roll axles, roll axle supports, as well as adjusting and fixing elements.
During the straightening of articles in these machines, the number of bends given to an article is determined not by the number of roll pairs, but by the rocking frequency of the rocking stands. The number of bends given to an article on machines with rocking stands is several times larger than on machines with stationary stands, which ensures higher quality straightening. However, machines with rocking stands have intrinsic disadvantages generated from large inertial masses of the rocking stands. The displacement of large masses leads to the creation of considerable dynamic loads, which impairs both the increase of oscillating frequency of rocking stands and the improvement of straightening quality and speed. This is particularly manifest in straightening large rolled shapes and tubes.
To ensure high quality straightening of substantially large rolled shapes and tubes it is necessary that the oscillating frequency of the rocking stands be increased. On the existing straightening machines with rocking stands it is impossible to obtain the required oscillating frequency due to the limitations stemmed from the design principle of these machines, characterized by the large masses of rocking stands and the complicated and bulky drive used for rocking the stands.
Straightening of large-size articles in the known machines leads to the enlargement of dimensions and masses of their rocking stands, which entails a still further increase of inertial masses and correspondingly the creation of considerable dynamic loads brought to bear on the components of the straightening machines. In their turn, with increasing oscillating frequency of rocking stands the dynamic loads in the machine units are increasing in square. All this restricts the abilities of straightening machines with rocking stands and makes it impossible to obtain the required quality of straightening especially in the case with large rolled shapes and tubes.
Thus, all the existing straightening machines come short of solving the problem of improving the quality of straightening with simultaneous speeding-up of the straightening process.